Most paragangliomas are either asymptomatic or present as a painless mass. While all contain neurosecretory granules, only in 1–3% of cases is secretion of hormones such as catecholamines abundant enough to be clinically significant; in that case manifestations often resemble those of pheochromocytomas (intra-medullary paraganglioma).

About 85% of paragangliomas develop in the abdomen; only 12% develop in the chest and 3% in the head and neck region (the latter are the most likely to be symptomatic). While most are single, rare multiple cases occur (usually in a hereditary syndrome). Paragangliomas are described by their site of origin and are often given special names:

- Carotid paraganglioma (carotid body tumor): Is the most common of the head and neck paragangliomas. It usually presents as a painless neck mass, but larger tumors may cause cranial nerve palsies, usually of the vagus nerve and hypoglossal nerve.

- Organ of Zuckerkandl: A collection of paraganglia near the bifurcation of the aorta, comprising a small mass of neural crest-derived chromaffin cells. Serves as a common origin of abdominal paragangliomas.

- Glomus tympanicum and Glomus jugulare: Both commonly present as a middle ear mass resulting in tinnitus (in 80%) and hearing loss (in 60%). The cranial nerves of the jugular foramen may be compressed, resulting swallowing difficulty, or ipsilateral weakness of the upper trapezius and sternocleiodomastoid muscles (from compression of the spinal accessory nerve). These patients present with a reddish bulge behind an intact ear drum. This condition is also known as the "Red drum". On application of pressure to the external ear canal with the help of a pneumatic ear speculum the mass could be seen to blanch. This sign is known as "Brown's sign". A deficient bony plate along the tympanic portion of the internal carotid artery (aberrant ICA) is a normal variant and can be mistaken with glomus jugulare.

- Vagal paraganglioma: These are the least common of the head and neck paragangliomas. They usually present as a painless neck mass, but may result in dysphagia and hoarseness.

- Pulmonary paraganglioma: These occur in the lung and may be either single or multiple.

- Other sites: Rare sites of involvement are the larynx, nasal cavity, paranasal sinuses, thyroid gland, and the thoracic inlet, as well as the bladder in extremely rare cases.

Pain is the most common symptom, followed by either sensorineural or conductive hearing loss, tinnitus or drainage (discharge). A mass lesion may be present, but it is often slow growing.

This tumor only affects the outer 1/3 to 1/2 of the external auditory canal as a primary site. If this area is not involved, the diagnosis should be questioned. The most common tumor type is ceruminous adenoid cystic carcinoma and ceruminous adenocarcinoma, NOS.

A nervous system neoplasm is a tumor affecting the nervous system. Types include:

- Nerve sheath tumor

- Brain tumor

- Arachnoid cyst

- Optic nerve glioma

The treatment is simple excision and exclusion of a malignant neoplasm.

Due to the diverse nature of salivary gland tumours, many different terms and classification systems have been used. Perhaps the most widely used currently is that system proposed by the World Health Organization in 2004, which classifies salivary neoplasms as primary or secondary, benign or malignant, and also by tissue of origin. This system defines five broad categories of salivary gland neoplasms:

Benign epithelial tumors

- Pleomorphic adenoma

- Warthin's tumor

- Myoepithelioma

- Basal cell adenoma

- Oncocytoma

- Canalicular adenoma

- Lymphadenoma

- "Sebaceous lymphadenoma"

- "Nonsebaceous lymphadenoma"

- Ductal papilloma

- "Inverted ductal papilloma"

- "Intraductal papilloma"

- "Sialadenoma papilliferum"

- Cystadenoma

- Malignant epithelial tumors

- Acinic cell carcinoma

- Mucoepidermoid carcinoma

- Adenoid cystic carcinoma

- Polymorphous low-grade adenocarcinoma

- Epithelial-myoepithelial carcinoma

- Clear cell carcinoma, not otherwise specified

- Basal cell adenocarcinoma

- Sebaceous carcinoma

- Sebaceous lymphadenocarcinoma

- Cystadenocarcinoma

- Low-grade cribriform cystadenocarcinoma

- Mucinous adenocarcinoma

- Oncocytic carcinoma

- Salivary duct carcinoma

- Salivary duct carcinoma, not otherwise specified

- Adenocarcinoma, not otherwise specified

- Myoepithelial carcinoma

- Carcinoma ex pleomorphic adenoma

- Mammary analogue secretory carcinoma

- Carcinosarcoma

- Metastasizing pleomorphic adenoma

- Squamous cell carcinoma

- Large cell carcinoma

- Lymphoepithelial carcinoma

- Sialoblastoma

- Soft tissue tumors

- Hemangioma

- Hematolymphoid tumors

- Hodgkin lymphoma

- Diffuse large B-cell lymphoma

- Extranodal marginal zone B cell lymphoma

- Secondary tumors (i.e. a tumor which has metastasized to the salivary gland from a distant location)

Others, not included in the WHO classification above, include:

- Intraosseous (central) salivary gland tumors

- Hybrid tumors (i.e. a tumor displaying combined forms of histologic tumor types)

- Hybrid carcinoma

- Others

- Others

- Keratocystoma

- Sialolipoma

Salivary gland tumours usually present as a lump or swelling in the affected gland which may or may not have been present for a long time. The lump may be accompanied by symptoms of duct blockage (e.g. xerostomia). Usually, in their early stages it is not possible to distinguish a benign tumour from a malignant one. One of the key differentiating symptoms of a malignant growth is nerve involvement. For example signs of facial nerve damage (e.g facial palsy) are associated with malignant parotid tumours. Facial pain, and paraesthesia are also very often associated with a malignant tumours. Other red flag symptoms which may suggest malignancy and warrant further investigation are fixation of the lump to the overlying skin, ulceration and induration of the mucosa.

Sebaceous lymphadenoma is a tissue diagnosis, e.g. salivary gland biopsy.

It may be confused with a number of benign and malignant neoplasms, including Warthin tumour, mucoepidermoid carcinoma and sebaceous lymphadenocarcinoma.

Malignant transformation to squamous cell carcinoma may occur, but is unusual.

The most common symptom of the papillary tumor is a headache. Because headaches are so common, most people think nothing of it. This is why brain tumors are so dangerous. There are not a lot of symptoms that go along with them so people tend to wait a long time before seeking medical help. Most of the time people will go see a doctor when their headaches become consistent and start to never go away. This symptom however occurs secondary to hydrocephalus, which is a result from compression of the cerebral aqueduct. The cerebral aqueduct is a narrow channel in the midbrain, which connects the third and fourth ventricles. When a tumor blocks the pathway of the cerebrospinal fluid, this will cause headaches in the patient. Often when hydrocephalus occurs, a shunt is put in place in order to alleviate the pressure. In one case study, an endoscopic third ventriculostomy was performed as a first line procedure to treat the hydrocephalus and also for diagnostic purposes.

In some cases, patients have had progressive diplopia, or double vision. Also, although not in all cases, patients sometimes suffer from nausea and vomiting.

Swelling is the most common presenting complaint; however, OKCs may be asymptomatic and found incidentally on dental X-rays.

Children affected by pilocytic astrocytoma can present with different symptoms that might include failure to thrive (lack of appropriate weight gain/ weight loss), headache, nausea, vomiting, irritability, torticollis (tilt neck or wry neck) difficulty to coordinate movements and visual complaints (including nystagmus). The complaints may vary depending on the location and size of the neoplasm. The most common symptoms are associated with increased intracranial pressure due to the size of the neoplasm.

Considered part of the PTEN hamartoma tumor syndrome (PHTS), which also includes Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, and Proteus-like syndrome, Cowden syndrome is a serious genetic disorder characterized by multiple hamartomas. Usually skin hamartomas exist, and commonly (in about 66% of cases) hamartoma of the thyroid gland exists. Additional growths can form in many parts of the body, especially in bones, CNS, the eyes, the genitourinary tract, the GI tract, and mucosa. The hamartomas themselves may cause symptoms or even death, but morbidity is more often associated with increased occurrence of malignancies, usually in the breast or thyroid.

Pancreatic serous cystadenoma, also known as serous cystadenoma of the pancreas and serous microcystic adenoma, a benign tumour of pancreas. It is usually found in the head of the pancreas, and may be associated with von Hippel-Lindau syndrome.

In contrast to some of the other cyst-forming tumors of the pancreas (such as the intraductal papillary mucinous neoplasm and the mucinous cystic neoplasm), serous cystic neoplasms are almost always entirely benign. There are some exceptions; rare case reports have described isolated malignant serous cystadenocarcinomas. In addition, serous cystic neoplasms slowly grow, and if they grow large enough they can press on adjacent organs and cause symptoms.

This lesion has been called a fetal lipoma, lipoma of embryonic fat or a lipoma of immature fat.

Patients present with a slow-growing, painless, solitary mass, usually of the subcutaneous tissues. It is much less frequently noted in the intramuscular tissue. It is not uncommon for symptoms to be present for years.

Benign neoplasm with "BROWN FAT" is noted.

Pathologists classify serous cystic neoplasms into two broad groups. Those that are benign, that have not spread to other organs, are designated "serous cystadenoma". Serous cystadenomas can be further sub-typed into microcystic, oligocystic (or macrocystic), solid, mixed serous-endocrine neoplasm, and VHL-associated serous cystic neoplasm. This latter classification scheme is useful because it highlights the range of appearances and the clinical associations of these neoplasms. Serous cystic neoplasms that have spread ("metastasized") to another organ are considered malignant and are designated "serous cystadenocarcinoma".

A neuroectodermal tumor is a tumor of the central or peripheral nervous system.

A hamartoma is a mostly benign, focal malformation that resembles a neoplasm in the tissue of its origin. While traditionally considered developmental malformation, many hamartomas have clonal chromosomal aberrations that are acquired through somatic mutations and on this basis are now considered to be neoplastic. It grows at the same rate as the surrounding tissue. It is composed of tissue elements normally found at that site, but they are growing in a disorganized manner. Hamartomas occur in many different parts of the body, and are most often asymptomatic incidentalomas (undetected until they are found incidentally on an imaging study obtained for another reason).

Additionally, the definition of hamartoma versus benign neoplasm is often unclear, since both lesions can be clonal. Lesions such as adenomas, developmental cysts, hemangiomas, lymphangiomas, and rhabdomyomas within the kidneys, lungs, or pancreas are interpreted by some experts as hamartomas while others consider them true neoplasms. Moreover, even though hamartomas show a benign histology, there is a risk of some rare but life-threatening clinical issues such as those found in neurofibromatosis type I and tuberous sclerosis.

It is different from choristoma, a closely related form of heterotopia. The two can be differentiated as follows: a hamartoma is an excess of normal tissue in a normal situation (e.g., a birthmark on the skin), while a choristoma is an excess of tissue in an abnormal situation (e.g., pancreatic tissue in the duodenum).

The tumor largely affects children under 15 years of age and about 20% only are found in adults with nearly 60% involving males and 40% females (1). The most frequent locations are head and neck (orbit and nasopharynx), central nervous system, abdomen and retroperitoneum, pelvis, perineum, scrotum and prostate(1). Clinical symptoms are not specific and usually caused by local tumor compression and infiltration.

A nerve sheath tumor is a type of tumor of the nervous system (nervous system neoplasm) which is made up primarily of the myelin surrounding nerves.

A peripheral nerve sheath tumor (PNST) is a nerve sheath tumor in the peripheral nervous system. Benign peripheral nerve sheath tumors include schwannomas and neurofibromas.

A malignant peripheral nerve sheath tumor (MPNST) is a cancerous peripheral nerve sheath tumor.

Ectomesenchymoma is a rare, fast-growing tumor of the nervous system or soft tissue that occurs mainly in children, although cases have been reported in patients up to age 60. Ectomesenchymomas may form in the head and neck, abdomen, perineum, scrotum, or limbs. Also called malignant ectomesenchymoma.

Malignant ectomesenchymoma (MEM) is a rare tumor of soft tissues or the CNS, which is composed of both neuroectodermal elements [represented by ganglion cells and/or well-differentiated or poorly differentiated neuroblastic cells such as ganglioneuroma, ganglioneuroblastoma, neuroblastoma, peripheral primitive neuroectodermal tumors – PNET] and one or more mesenchymal neoplastic elements, usually rhabdomyosarcoma . The most accepted theory suggests that this tumor arises from remnants of migratory neural crest cells and thus from the ectomesenchyme.

Neurocutaneous melanosis is associated with the presence of either giant congenital melanocytic nevi or non-giant nevi of the skin. It is estimated that neurocutaneous melanosis is present in 2% to 45% of patients with giant congenital melanocytic nevi. Patients with non-giant congenital melanocytic nevi seem to have a much lower, but undefined risk. Of these patients, only a small number are symptomatic, usually displaying symptoms before the age of 2.

These symptoms are the result of melanocytic lesions being present in the leptomeninges of the central nervous system.

Symptoms can include:

- Papilledema

- Cranial palsies

- Headache

- Vomiting

- Seizures

Others symptoms may also exist that are related to an increase in intracranial pressure. These symptoms seem to be present regardless of the malignancy of the melanin deposits within the central nervous system.

Approximately 10% of patient with neurocutaneous melanosis also present the Dandy–Walker syndrome and associated Dandy-Walker malformation. This malformation involves an enlargement of the posterior fossae and fourth ventricle along with agenesis of the cerebellar vermis. The abnormalities of the leptomeninges during fetal development due to neurocutaneous melanosis may be the cause of this increased incidence of the Dandy-Walker malformation. The development of hydrocephalus is the most common symptom associated with a combination of neurocutaneous melanosis and a Dandy-Walker malformation, occurring in about two out of three patients.

Papillary tumors of the pineal region (PTPR) were first described by A. Jouvet et al. in 2003 and were introduced in the World Health Organization (WHO) classification of Central Nervous System (CNS) in 2007. Papillary Tumors of the Pineal Region are located on the pineal gland which is located in the center of the brain. The pineal gland is located on roof of the diencephalon. It is a cone shaped structure dorsal to the midbrain tectum. The tumor appears to be derived from the specialized ependymal cells of the subcommissural organ. Papillary tumors of the central nervous system and particularly of the pineal region are very rare and so diagnosing them is extremely difficult.